I have thin sections of rock collected from a crater in which i find closely spaced parallel cleavages in quartz grains. I wish to understand the result of tectonics or shock metamorphism by impact crater.
May I recommend two links dealing among others with quartz microstructures due to shock metamorphism:
http://www.impact-structures.com/impact-spain/the-azuara-impact-structure/shock-effects-shock-metamorphism-in-rocks-from-the-azuara-impact-structure/
http://www.impact-structures.com/2011/12/are-bent-planar-deformation-features-pdfs-no-pdfs/
Tectonically deformed quartz grains would have no cleavage-like lines within the crystal (would be smooth instead), only much much higher power shock from a meteor impact will show these lines, I would think.
Thank you prof Guenter. I have gone through the links.
I have results similar to the crater given in the link.
However, i am seriously in dilemma how to confirm it as it has been controversial, said by prof mark.
Thank you Prof Mark. Could you suggest any exact method to identify the sugnatures of meteroritic impact? Also, how to identify it through petrography!
Many thanks prof Michael. Yes indeed ! My results show two sets of cleavage in cleavage having distance betwen two cleavage planes ~20micron. However, i wish to add some more evidences. Please suggest what else can be done to prove it.
Dear Mark,
In my reply I have less emphasis on the text but much more on the micro photos just for comparison.
However, please call me issues on the subject of impact that are not controversial.
Best regards,
Guenter
If qtz is formed within a tectonic environment, not only will be smooth, but will also have undulose extinction which *may* be oriented in the direction of stress. During impact, the crystal will break and show cleavage (not seen in regular qtz), and may even display shock veins of amorphous material. I hope this helps.
Regards,
Fernanda
Search for high pressure mineral (coesite) and Planar Deformation Feature (PDF) in quartz. This is very fundamental tool to identify the meteoritic impact. You can also try to search glass of mineral or rock.
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